Question

I’m writing a package installer script in Perl. I need a command (probably OS command) that returns a simple 0 or 1 to the caller script if a Ubuntu/Debian package is installed or not.

I’ve tried

      dpkg -s

It always returns 0.

      dpkg -L 

almost works but if the user does not

      apt-get --purge remove 

the packages, some files are left and always returns 0

I don’t want to grep text – a simple true or false is what I need.
Any ideas?

@Andy:

   aptitude remove unixodbc -y

   dpkg-query -W unixodbc; echo $?
   unixodbc        2.2.11-21
   0

   aptitude install unixodbc -y

   dpkg-query -W unixodbc; echo $?
   unixodbc        2.2.11-21
   0

Answer 1

Maybe not ideal, but this works:

dpkg -s "$package" | grep '^Status:' | grep -q ' installed'

Or just

dpkg -s "$package" | grep -q '^Status:.* installed'